Fabrication Of Metal-Organic Frameworks-Derived Composites And Their Application In Electrochemical Sensors

Metal-organic frameworks(MOFs),a new class of porous materials resulting from the bonding of metal ions with polyfunctional organic ligands,have good application potential in bio-sensing,catalysis,drug delivery,gas separation and storage due to their large specific surface area,diverse structural,and highly ordered pore structure.Recently,MOFs based composites also receive much attention in electrochemical sensing field.However,the preparation methods of MOFs-derived materials are tedious,and the obtained materials show poor catalytic performance besides the limited species,which restricts its application.Considering these points,we tried to simplify the synthesis procedures and improve the catalytic property of the MOFs-derived materials.The main contents are summarized as follows:1.One-step synthesis of copper-based metal-organic framework-graphene nanocomposite for electrochemical sensor of hydrogen peroxide and ascorbic acid.A copper-based metal-organic framework/graphene nanocomposite(Cu-MOF/GN)(Cu3(BTC)2,BTC = 1,3,5-benzene-tricarboxylate)was prepared by a facile one-step method for the first time.Unlike the conventional strategies,in this procedure graphene oxide was reduced to GN by an endogenous reducing agent produced by dimethylformamide,which was used as solvent in the synthesis of Cu-MOF.The addition of GN could improve the electrical conductivity of composite and restrict the crystal growth and reunion of Cu-MOF.Moreover,the nanocomposite exhibited high stability due to the hydrogen bonding,π-π stacking and Cu-0 coordination between Cu-MOF and GN.Owing to the synergetic effect of Cu-MOF and GN,the Cu-MOF/GN nanocomposite showed high electrocatalytic activity.When it was used for constructing H2O2 and ascorbic acid sensor,it presented good performance.2.Highly dispersed AuPd alloy nanoparticles immobilized on UiO-66-NH2 metal-organic framework for the detection of nitriteHighly dispersed AuPd alloy nanoparticles(NPs,3-6 nm)decorated amino-functionalized Zr(IV)-based metal-organic framework(UiO-66-NH2)[i.e.Zr6O4(OH)4(BDC-NH2)6,BDC = 1,4-benzenedicarboxylate]was prepared via a novel adsorption/reduction method in ethanol-water solution.In this process,the UiO-66-NH2 acted as both supporting platform and protective agent.The pores of UiO-66-NH2 could limit the aggregation and migration of AuPd alloy NPs.The resulting AuPd/UiO-66-NH2 catalyst possessed large specific surface area and excellent stability and dispersity in aqueous media.When it was used to construct a nitrite sensor,the electrochemical study demonstrated that the AuPd/UiO-66-NH2 sensor had an extended linear response concentration range of 0.05-5666 μmol·L-1 for nitrite detection,with a detection limit of 0.01 μmol·L-1.It was successfully applied to determine nitrite in sausage and pickle samples.3.Core-shell CuxO nanoparticles@ZIF-8 composite for highly selective electrochemical sensing of hydrogen peroxideA novel core-shell heterostructure of CuxO nanoparticles@zeolitic imidazolate framework(CuxO NPs@ZIF-8)[ZIF-8,i.e.Zn(MIM)2,HMIM = 2-methylimidazole]was successfully prepared through facile pyrolysis of nanocrystalline copper-based metal-organic framework[nHKUST-1,i.e.Cu3(BTC)2(BTC ＝1,3,5-benzene-tricarboxylate)]＠ZIF-8,based on the different thermal stability of the two metal-organic frameworks(MOFs).The small CuxO NPs derived from nHKUST-1 uniformly dispersed inside the host material and provided active sites,while ZIF-8 kept the original structure as molecular sieving shell.Owing to the proper pore shape and pore size of ZIF-8,H2O2 could diffuse through the shell,but bigger molecules could not pass.Thus the composite material exhibited high selectivity when it was used to construct a H2O2 sensor.In addition,the sensor showed extended linear detection range(from 1.5 to 21442 μmol·L-1),low detection limit(0.15μmol·L-1)and high sensitivity.4.Well-defined gold nanoparticles@N-doped porous carbon prepared from metal nanoparticles@metal-organic frameworks for electrochemical sensing of hydrazineA composite material of Au nanoparticles(Au NPs)encapsulated in N-doped porous carbon(Au@NPC)was prepared through a one-pot thermolysis of Au NPs@zeolitic imidazolate framework(Au@ZIF-8)precursor.The obtained Au@NPC possessed high specific surface area as well as superior thermal and chemical stability.The NPC shell functioned as a barrier to effectively prevent Au NPs from dissolution,migration and aggregation during carbonization process and electrochemical testing,while it allowed the transit of electrolyte to the Au NPs surface.The core—shell structure and Au content was related to the preparation conditions.When the concentration of Au NPs was 0.5 mg·mL-1,the resulting Au@ZIF-8 could be carbonized to form well core-shell structure.The size of encapsulated multi-core Au NPs slightly increased with enhancing carbonizing temperature(e.g.from 600 to 800 ℃),while the Au content and surface area of the obtained composite material also increased.On this basis,a sensitive and stable electrochemical sensor was constructed for the detection of hydrazine.Under the optimized conditions,a linear dynamic range of 80-466.28 p.mol·L-1,with a satisfactory sensitivity of 2035,4μ/mmol·L-1 cm2 and a comparable detection limit of 8 nmol·L-1(S/N = 3),was obtained.5.Metal-organic framework derived hollow polyhedron CuCo2O4 functionalized porous graphene for sensitive glucose sensingA hollow CuCo2O4 polyhedron/porous reduced graphene oxide(PrGO)composite was prepared by simple thermolysis-induced transformation of heterobimetallic zeolitic imidazolate frameworks/porous graphene oxide(Cu-Co-ZIFs/PGO).In the obtained composite,PrGO sheets not only provided conduction path,but also served as protective agent to prevent the aggregation of crystals.The hollow rhombic dodecahedral CuCo2O4 possessed plentiful active sites and high electrocatalytic activity.When the composite was optimized and used for glucose sensing,it displayed good performance with a wide linear range of 0.5-3354μmol·L-1,a low detection limit of 0.15 μmol·L-1(S/N = 3),a high sensitivity of 2426μA/mol·L-1·cm2.Moreover,the sensor possessed desirable selectivity,it was successfully applied to the determination of glucose content in human serum samples and the recovery was 92.3%to 108.4%.